This invention generally relates to disk brakes, clutches and the like, and more particularly to a method and means for fastening friction wear pads or cups to opposite faces of a disk core member. The cups contain a body of embedded friction material which may be any of the well known metallic friction lining materials including sintered friction materials.
Heretofore, when two wear pads of friction material were mounted on opposing faces of a disk core, they were attached by means of various type fasteners including snap type fasteners, rivets, force-fit fasteners and the like. Prior art fasteners of the type alluded to are illustrated in the drawing FIGS. 1(a)-1(f) of FIG. 1. FIGS. 1(a) and 1(c) show snap and force-fit fasteners respectively, and these types are generally not suitable in harsh environments such as for example, aircraft and heavy equipment environments, because they tend to loosen under the extremes of temperature, especially under the high heat associated with braking of these type vehicles. Loose wear pads are subject to uneven pressure across the face of the friction material causing uneven wear and thus a requirement for premature replacement. FIG. 1(b) illustrates the application of rivets to mounting to the wear pads and in this case an access hole must be provided in the friction material so that the rivet may be inserted therein and through the core member to the opposite pad. Holes in the friction material reduce the area of the friction surface available and also tend to cause an uneven pressure distribution over the face of the material which results in uneven and increased wear and again a requirement for premature replacement. FIG. 1(e) illustrates spot welding of the friction pads wherein a depression on the bottom of one pad is in intimate contact with a like depression in another pad mounted on the opposite surface of the core and electrodes are positioned within the two interconnected depressions such as to effect a spot weld of the two pads. In this instance, access holes must also be provided in the friction material so that electrodes may be inserted in each pad depression. Holes in the friction material have adverse wear effects as herebefore stated with respect to the rivet configuration of FIG. 1(b). FIG. 1(d) illustrates a resistance welded assembly wherein the friction pads are again formed with a depression in the bottom surface such that when two pads are mounted on opposite faces of the core member, the depressions are in intimate contact within an access hole in the core. In this instance, a sintered metallic friction lining material is embedded in the pad cup with a metal plug seated within the depression such that a complete current path exists from the surface of the friction material on one side of the core to the surface of the friction material on the opposite side of the core. Electrodes placed on the surfaces of the friction material effect a current through the assembly such that the contacting depressions are resistance welded together. A disadvantage of this technique is the fact that the weld in the area of the depressions is a small area contact and the pads must be carefully positioned so as to be welded in faced parallel alignment. Furthermore, the depressions must be of the proper depth for a particular core thickness and metal plugs or inserts must be positioned in the depressions such that a current path exists between the two. FIG. 1(f) shows another embodiment wherein steel buttons are first welded to the bottoms of the wear pads and these are then inserted in a core access hole and resistance welded together. A disadvantage of this technique is the fact multiple weld operations are required and the weld contact area is small. Furthermore, the depth of the buttons at the first weld must be maintained such that parallelism of the pads on the core is not affected during the second weld and the pads are securely affixed to the core. Descriptions and details of the above-mentioned prior art may be had in the following respective U.S. Pat. Nos.: 4,076,106; 3,724,614; 3,710,914; 3,913,716; and 3,982,612.
An object of the present invention therefore is to provide a friction component for brakes, clutches and the like, wherein a friction pad is provided having a continuous friction surface across its face and a flat bottom surface to provide an increased friction surface area and depth of friction material.
Another object of the invention is to provide friction pads on opposing surfaces of a disk core member that are projection welded in a manner to give a greater contact weld area between the two pads and thus a more stable mounting on the core.
Still another object of the invention is to provide a metallic bushing for projection welding of the opposing friction pads such that they may be applied to any thickness core member by merely changing the length of the bushing.
The invention further provides weld bushings that may be increased in diameter for an increased stable mounting of the friction pads on the core member.